Method of removing upper internals from a nuclear reactor pressurized vessel

ABSTRACT

A lifting fixture for removing the upper internals from a nuclear reactor to provide access to the core during a refueling that does not require flooding of a refueling canal. A shield plate is integral to a lifting rig used to remove the upper internals. The shield plate is sized to be supported on the reactor vessel upper flange and to cover the reactor vessel opening with the closure head removed. The shield plate has openings that are in-line with the control rod assembly drive rod travel housings. Control rod assembly drive rods can be accessed through the openings. The lifting rig allows personnel to decouple the drive rods from the rod cluster control assemblies. The lifting fixture enables the decoupled drive rods to be lifted from the core with the upper internals, while shielding maintenance personnel without flooding the area above the reactor.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of and claims priority toU.S. patent application Ser. No. 13/741,737, filed Jan. 15, 2013entitled APPARATUS AND METHOD FOR REMOVING THE UPPER INTERNALS FROM ANUCLEAR REACTOR PRESSURIZED VESSEL.

BACKGROUND

1. Field

This invention pertains generally to an apparatus and a method forrefueling a nuclear reactor and more particularly to such an apparatusand method for removing and reinstalling the upper internals of such areactor.

2. Related Art

A pressurized water reactor has a large number of elongated fuelassemblies mounted within an upright reactor vessel. Pressurized coolantis circulated through the fuel assemblies to absorb heat generated bynuclear reactions in fissionable material contained in the fuelassemblies. The primary side of such a nuclear reactor power generatingsystem which is cooled with water under pressure comprises an enclosedcircuit which is isolated from and in heat exchange relationship with asecondary circuit for the production of useful energy. The primary sidecomprises the reactor vessel enclosing a core internal structure thatsupports the plurality of fuel assemblies containing the fissilematerial, the primary circuit within heat exchange steam generators, theinner volume of a pressurizer, pumps and pipes for circulatingpressurized water; the pipes connecting each of the steam generators andpumps to the reactor vessel independently. In conventional nuclearplants of that type each of the parts of the primary side comprising thesteam generator, a pump and a system of pipes which are connected to thereactor vessel form a loop of the primary side.

For the purpose of illustration, FIG. 1 shows a simplified conventionalnuclear reactor primary system, including a generally cylindricalpressure vessel 10 having a closure head 12 enclosing a nuclear core 14.A liquid coolant, such as water or borated water, is pumped into thevessel 10 by pump 16 through the core 14 where heat energy is absorbedand is discharged to a heat exchanger 18, typically referred to as asteam generator, in which heat is transferred to a utilization circuit(not shown), such as a steam driven turbine generator. The reactorcoolant is then returned to the pump 16, completing the primary loop.Typically, a plurality of the above-described loops are connected to asingle reactor vessel 10 by reactor coolant piping 20.

An exemplary conventional reactor design is shown in more detail in FIG.2. In addition to the core 14 comprised of a plurality of parallel,vertical co-extending fuel assemblies 22, for the purpose of thisdescription, the other vessel internal structures can be divided intothe lower internals 24 and the upper internals 26. In conventionaldesigns, the lower internals function to support, align and guide corecomponents and instrumentation as well as direct flow within the vessel.The upper internals restrain or provide a secondary restraint for thefuel assemblies 22 (only two of which are shown for simplicity in FIG.2), and support and guide instrumentation and components, such ascontrol rods 28. In the exemplary reactor shown in FIG. 2, coolantenters the reactor vessel through one or more inlet nozzles 30, flowsdown through an annulus between the reactor vessel and the core barrel32, is turned 180° in a lower plenum 34, passes upwardly to a lowersupport plate 37 and a lower core plate 36 upon which the fuelassemblies are seated and through and about the fuel assemblies 22. Insome designs, the lower support plate 37 and the lower core plate 36 arereplaced by a single structure, a lower core support plate having thesame elevation as 37. The coolant flow through the core and surroundingarea 38 is typically large on the order of 400,000 gallons per minute ata velocity of approximately 20 feet per second. The resulting pressuredrop and frictional forces tend to cause the fuel assemblies to rise,which movement is restrained by the upper internals, including acircular upper core plate 40. Coolant exiting the core 14 flows alongthe underside of the upper core plate 40 and upwardly through aplurality of perforations 42. The coolant then flows upwardly andradially to one or more outlet nozzles 44.

The upper internals 26 can be supported from the vessel or the vesselhead and include an upper support assembly 46. Loads are transmittedbetween the upper support assembly 46 and the upper core plate 40,primarily by a plurality of support columns 48. A support column isaligned above a selected fuel assembly 22 and perforations 42 in theupper core plate 40.

Rectilinearly moveable control rods 28 which typically include a driveshaft or drive rod 50 and spider assembly 52 of neutron poison rods, areguided through the upper internals 26 and into aligned fuel assemblies22 by control rod guide tubes 54. The guide tubes are fixedly joined tothe upper support assembly 46 and the top of the upper core plate 40.The support column 48 arrangement assists in retarding guide tubedeformation under accident conditions which could detrimentally affectcontrol rod insertion capability.

To control the fission process a number of control rods 28 arereciprocally moveable in guide thimbles located at predeterminedpositions in the fuel assemblies 22. Specifically, a control rodmechanism positioned above the top nozzle of the fuel assembly supportsa plurality of control rods. The control rod mechanism (also known as arod cluster control assembly) has an internally threaded cylindrical hubmember with a plurality of radially extending flukes or arms that formthe spider assembly 52 previously noted with regard to FIG. 2. Each armis interconnected to a control rod 28 such that the control rod assemblymechanism 72 is operable to move the control rods 28 vertically withinguide thimbles within the fuel assemblies to thereby control the fissionprocess in the fuel assembly 22, under the motive power of the controlrod drive shaft 50 which is coupled to the control rod mechanism hub,all in a well known manner.

Nuclear power plants which employ light water reactors require periodicoutages for refueling of the reactor. New fuel assemblies are deliveredto the plant and are temporarily stored in a fuel storage building,along with used fuel assemblies which may have been previously removedfrom the reactor. During a refueling outage, a portion of the fuelassemblies in the reactor are removed from the reactor to the fuelstorage building. A second portion of the fuel assemblies are moved fromone support location in the reactor to another core support location inthe reactor. New fuel assemblies are moved from the fuel storagebuilding into the reactor to replace those fuel assemblies which wereremoved. These movements are done in accordance with a detailed sequenceplan so that each fuel assembly is placed in a specific location inaccordance with an overall refueling plan prepared by the reactor coredesigner. In conventional reactors, the removal of the reactor internalcomponents necessary to access the fuel and the movement of new and oldfuel between the reactor and the spent fuel pool in the spent fuelstorage building is performed under water to shield the plantmaintenance personnel. This is accomplished by raising the water levelin a refueling cavity and canal that is integral to the plant's buildingstructure. The water level of more than 20 feet provides shielding forthe movement of the reactor internal structures and the fuel assemblies.

Refueling activities are often on a critical path for returning thenuclear plant to power operation, therefore, the speed of theseoperations is an important economic consideration for the power plantowner. Furthermore, the plant equipment and fuel assemblies areexpensive and care must be taken not to cause damage or unnecessaryradiation exposure due to improper handling of the fuel assemblies orfuel transfer equipment. The precision of these operations is alsoimportant since the safe and economical operation of the reactor coredepends upon each fuel assembly being in its proper location. A typicalpressurized water reactor needs to be refueled every 18 to 24 months.

Commercial power plants employing the conventional designs illustratedin FIGS. 1 and 2 are typically on the order of 1,100 megawatts or more.More recently, Westinghouse Electric Company LLC has proposed a smallmodular reactor in the 200 megawatt class. The small modular reactor isan integral pressurized water reactor with all primary loop componentslocated inside the reactor vessel. The reactor vessel is surrounded by acompact, high pressure containment. Due to both the limited space withinthe containment and the low cost requirement for integral pressurizedlight water reactors, the overall number of auxiliary systems needs tobe minimized without compromising safety or functionality. For example,the compact, high pressure containment associated with a design of somesmall modular reactors does not allow for the incorporation of a largefloodable cavity above the reactor vessel in which the transferredcomponents can be shielded.

Accordingly, it is an object of this invention to provide specialhandling equipment to remove the upper internals to permit access to thefuel assemblies, without flooding the containment, while protecting theplant personnel and adjacent equipment from the harmful effects ofradiation.

It is a further object of this invention to provide such equipment thatcan also be employed with conventional reactors that will avoid thenecessity and the time and expense of flooding and draining thecontainment during a refueling operation.

SUMMARY

These and other objects are achieved by an upper internals packagelifting fixture for refueling a reactor having a reactor vessel with anupper flange surrounding an opening in the reactor vessel that is sealedby a mating flange on a closure head. The reactor vessel encloses anupper internals package that seats above a plurality of fuel assemblieswithin a core of the reactor. The upper internals package includescontrol rod assembly drive rod travel housings in which control rodassembly drive rods are housed and through which the drive rods travelalong a vertical path. The upper internal package lifting fixturecomprises a shield plate sized to cover the opening in the reactorvessel when supported on the reactor vessel upper flange. The shieldplate is formed from a material that lessens the radiation exposure ofworkers working above the shield plate covering the reactor vesselopening. A lifting rig is formed integral with and extends above theshield plate and means are provided for attaching the shield plate tothe upper internals package that can be withdrawn from the reactor byraising the lifting rig.

Preferably, the shield plate of the upper internals package liftingfixture includes openings to access the control rod assembly drive rodsand desirably the openings include a tubular penetration through theshield plate that align and mate with the rod travel housings in theupper internals package. In one embodiment, the tubular penetrationsrespectively include a conical guide that engages the corresponding rodtravel housing. Preferably, a number of the tubular penetrations includea drive rod latching tool that is reciprocally moveable within thetubular penetrations and is configured to couple with one or more of thedrive rods and disconnect the respective drive rods from a correspondingcontrol rod assembly. Desirably, a retainer is provided that maintains aposition of the drive rod latching tool in the tubular penetration.Preferably, the lifting fixture includes a hoist configured to raise andlower the drive rod latching tool wherein the hoist has sufficient powerto do so with the drive rod, decoupled from the control rod assembly,attached to the drive rod latching tool and preferably, the hoist is anintegral part of the lifting fixture.

In another embodiment, the shield plate includes a ventilation andfiltration system configured to draw air from below the shield plate,filter the air so drawn to remove radioactive contaminants and exhaustthe drawn air above the shield plate. Furthermore, one embodiment of theupper internals package lifting fixture includes means to engagealignment studs in the upper flange of the vessel to align the shieldplate as it is being lowered onto the reactor vessel.

In still another embodiment wherein the rod travel housings extend abovethe upper flange of the reactor vessel, the shield plate is formed in atop hat configuration to span the reactor vessel opening above the rodtravel housings and has a radially outwardly extending brim that issupported on the upper flange of the reactor vessel.

In addition, preferably the upper internals package lifting fixtureincludes a shielded cylinder having an inner diameter that is largerthan an outer diameter of the shield plate, a narrowed opening in anupper end that has a smaller diameter than the outer diameter of theshield plate and a length that is substantially equal to or longer thanthe upper internals package. Desirably, the shielded cylinder isslidably positioned over the shield plate and the lifting rig has anouter diameter that is smaller than the narrowed opening in the upperend of the shielded cylinder.

This invention further contemplates a method of removing an upperinternals package from a nuclear reactor having a reactor vessel with anupper flange surrounding an opening in the reactor vessel that is sealedby a mating flange on a closure head. The reactor vessel encloses theupper internals package that seats above a plurality of fuel assemblieswithin a core of the reactor. The upper internals package includes aplurality of rod travel housings in which control rod assembly driverods are housed and through which the drive rods travel along a verticalpath. The method comprises the step of removing the closure head fromthe reactor vessel. The method then lowers a shield plate over theopening in the reactor vessel; the shield plate being sized to cover theopening when supported on the reactor vessel upper flange and formedfrom a material that lessens the radiation exposure of workers workingabove the shield plate covering the reactor vessel opening. The shieldplate includes an integral lifting rig extending above an upper surfacethereof. The method then attaches the shield plate to the upperinternals package and raises the shield plate to withdraw the upperinternals package out of the reactor.

In one embodiment, the shield plate includes openings to access thecontrol rod assembly drive rods; the access openings including a driverod latching tool that is reciprocally movable along a substantiallyvertical travel path through the opening and into the rod travelhousings to connect to the drive rods and decouple the drive rods fromthe corresponding control rod assemblies. The method further includesthe steps of attaching the drive rod latching tool at least to one ofthe drive rods; decoupling the drive rod from the corresponding controlrod assembly; and raising the drive rod latching tool to raise the driverod within the rod travel housing. Preferably, before the step ofraising the shield plate, the method includes the step of lowering ashielded cylinder over the shield plate and around the upper internalspackage. Desirably, the shielded cylinder is supported from the shieldplate when the shield cylinder is fully lowered around the upperinternals package.

In still another embodiment, the method includes the step of maintaininga negative atmosphere within the shielded cylinder. Preferably, the stepof maintaining a negative atmosphere within the shield cylindercomprises venting air from within the shielded cylinder and filteringthe vented air before being exhausted outside the shielded cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the invention can be gained from thefollowing description of the preferred embodiments when read inconjunction with the accompanying drawings in which:

FIG. 1 is a simplified schematic of a conventional nuclear reactorsystem to which the embodiments described hereafter can be applied;

FIG. 2 is an elevational view, partially in section, of a nuclearreactor vessel and internal components to which the embodimentsdescribed hereafter can be applied;

FIG. 3 is a perspective view, partially cut away, showing a smallmodular reactor system;

FIG. 4 is an enlarged view of the reactor vessel shown in FIG. 3;

FIG. 5 is a schematic cross sectional view of the reactor vessel shownin FIG. 4 with the steam generator removed and the reactor coolant levellowered to the level of the closure flange;

FIG. 6 is a schematic cross sectional view of the reactor vessel shownin FIG. 5 with the lifting rig and shield plate attached as an integralassembly to the penetration flange of the upper internals;

FIG. 7 is the schematic reactor cross sectional view shown in FIG. 6with the decoupling tool of this invention lowered until it engages acontrol rod;

FIG. 8 is the schematic reactor cross sectional view shown in FIG. 7showing the decoupling tool decoupling the drive rod from a rod clustercontrol assembly in accordance with one embodiment described hereafter;

FIG. 9 is the reactor cross sectional view shown in FIG. 8 with ashielded cylinder being lowered over the integral shield plate liftingrig assembly;

FIG. 10 is the schematic reactor cross sectional view shown in FIG. 9with the internals package being lifted from the reactor vessel; and

FIG. 11 is a perspective view, partially in section, showing thecomplete upper internals package lifting fixture of this invention withthe reactor upper internals engaged.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 3 and 4 illustrate a small modular reactor design available fromthe Westinghouse Electric Company LLC, Cranberry Township, Pa., to whichthis invention may be applied, though it should be appreciated that theinvention can also be applied to a conventional pressurized waterreactor such as the one illustrated in FIGS. 1 and 2. FIG. 3 shows aperspective view of the reactor containment 11, partially cut away, toshow the pressure vessel 10 and its internal components. FIG. 4 is anenlarged view of the pressure vessel shown in FIG. 3. The pressurizer 58is common to most pressurized water reactor designs, though not shown inFIG. 1, and is typically included in one loop to maintain the system'spressure. In the small modular reactor design illustrated in FIGS. 3 and4 the pressurizer 58 is integrated into the upper portion of the reactorvessel head 12 and eliminates the need for a separate component. Itshould be appreciated that the same reference characters are employedfor corresponding components among the several figures. A hot leg riser60 directs primary coolant from the core 14 to a steam generator 18which surrounds the hot leg riser 60. A number of cooling pumps 16 arecircumferentially spaced around the reactor vessel 10 at an elevationnear the upper end of the upper internals 26. The reactor coolant pumps16 are horizontally mounted axial flow canned motor pumps. The reactorcore 14 and the upper internals 26, except for their size, aresubstantially the same as the corresponding components previouslydescribed with regard to FIGS. 1 and 2. From the foregoing, it should beappreciated that employing the traditional refueling method by floodingthe reactor well above the area of the vessel flange 64 and transferringthe fuel assemblies under water to a spent fuel pool by way of atransfer canal 62 that extends through the containment 11 would not bepractical with this type of containment and compact design. A furtherunderstanding of the operation of the small modular reactor illustratedin FIGS. 3 and 4 can be found in U.S. patent application Ser. No.13/495,050, filed Jun. 13, 2012, entitled “Pressurized Water ReactorCompact Steam Generator.”

This invention provides a means of shielding and ventilating the upperinternals package 26 as it is removed from the reactor vessel 10 that isintegral to the lifting rig used to remove the upper internals package.The invention also provides a means for personnel to decouple the driverod 50 from the rod cluster control assemblies 72 which is required forrefueling pressurized water reactors. However, before the upperinternals package can be accessed the reactor head 12 has to be removedand the coolant level 96 within the reactor vessel 10 has to be loweredto the level of the reactor flange 64, as shown in FIG. 5. Once the headis removed and the coolant level is lowered a fixture can be positionedto lift the upper internals package 26 out of the reactor vessel.

One embodiment of the lifting fixture 76 of this invention for thispurpose is illustrated in FIGS. 6-11 and includes a thickened shieldplate 78 that is placed over the open reactor vessel prior to removingthe upper internals. The thickened shield plate provides radiationshielding and access to the control rod drive rods 50 that arereciprocally movable within the rod travel housings 80. Access to thedrive rods is provided through aligned openings 82 in the shield plate78. A means of attaching the shield plate 78 to the upper internalsassembly is provided so that the upper internals assembly is lifted withthe shield plate. In the embodiment illustrated in FIGS. 6-8, the shieldplate 78 is attached to an intermediate penetration flange 66 from whichthe upper internals are suspended. The intermediate penetration flange66 is more fully described in co-pending application Ser. No.13/457,683, filed Apr. 27, 2012, entitled “Instrumentation and ControlPenetration Flange for Pressurized Water Reactor.”

Tubular penetrations 84 extend through the openings 82 in the shieldplate 78 with conical guides 85 that respectively engage one of the rodtravel housings 80 of the control rod drive assembly. Though the guidesare described as conical, it should be appreciated that they may have astepped configuration or any of the geometry that will guide the tubularpenetrations 84 over the rod travel housings 80. A lifting rig 86 whichis integral to the shield plate 78 is designed to lift the upperinternals 26 and the drive rod assemblies 50 from the reactor vessel 10during refueling. A number of drive rod latching tools 88 are providedthat are staged in the tubular penetrations 84 of the shield plate 78. Ahoist 90 is integral to the lifting rig 86 and is used to raise thedrive rod assemblies 50 after they have been decoupled from the rodcluster control assemblies 72, employing the latching tools 88 which arefirst lowered by the hoist 90 to couple with the upper ends of the driverods 50. A retaining clip 92 maintains the desired position of the driverod latching tool 88 in the penetration tube 84. A ventilation system 94(shown only in FIG. 11) is also integral to the lifting fixture 76 andis configured to maintain filter ventilation of the upper internals asthey dry out and reduce the potential for airborne contamination. Ameans is also provided to engage alignment studs in the vessel to alignthe upper internals lifting fixture assembly 76 as it is being loweredonto the reactor vessel.

During refueling, the upper internals 26 are removed to gain access tothe fuel. Before the internals can be removed, the reactor isdepressurized and the reactor closure head or in the case of many smallmodular reactor designs, the steam generator and pressurizer are removedby removing the bolts 74 that anchor the reactor head flange 68 to thepenetration flange 66 and the reactor vessel flange 64. At this point inthe refueling of a traditional pressurized water reactor, the refuelingcavity is flooded and the drive rods are decoupled from the rod controlcluster assemblies and removed from the upper internals.

Small modular reactors with integral pressurized water reactors andcompact containments may require that the drive rods are decoupled fromthe rod cluster control assemblies without the shielding benefit of aflooded refueling cavity. This invention allows for personnel todecouple the drive rods while shielded from the activated components ofthe reactor internals. Subsequently, the invention allows removal of theupper internals using an integral lifting rig while ensuring that theactivated components are shielded during the lift.

FIGS. 5 through 10 illustrate how the invention is used during reactordisassembly. The reverse process is used during reactor assembly.

FIG. 5 shows an integral reactor with the steam generator removed andthe reactor coolant water level 96 lowered to the level of the reactorvessel closure flange 64. In this design, the rod travel housings 80 ofthe control rod drive mechanisms 50 extend above the water level. Asshown, the control rod cluster assemblies 72 are completely insertedinto the fuel assemblies 22 of the reactor core.

FIG. 6 shows the lifting rig 86 and the shield plate 78 (as an integralassembly) attached to the penetration flange 66 of the upper internals26. Though the lifting rig 86 and the shield plate 78 are described asan integral unit, it should be appreciated that they may be constructedas separate parts and joined at their interface by any suitableattaching means such as by bolting or welding to form one unit. Theshield plate 78 is configured in a top hot design having an upper planarsurface 98 that spans the opening in the reactor above the rod travelhousings, vertical legs 100 and a radially outwardly extending rim orflange 102 that rests upon and is attached to the penetration flange 66.The top hat design enables the shield plate 78 to accommodate the heightof the rod travel housings 80, though it should be appreciated that forreactor internals designs in which the rod travel housings do not extendabove the connection point between the shield plate and the upperinternals, the shield plate 78 may assume a generally planarconfiguration rather than the top hat design. The lifting legs 104 onthe lifting rig 86 extend through the stud clearance holes in thepenetration flange 66 and are secured to the flange with an appropriatefastener such as a threaded collar, a hitch pin or C-shaped clamp. Theopenings 82 in the shield plate 78 and the tubular penetrations 84 allowaccess to the drive rod drive shafts for decoupling from the rod clustercontrol assemblies 72. These same penetrations support the couplingtools 88 within the integral lifting fixture assembly 76 during storageand handling. The shield plate 78, tubular penetrations 84 anddecoupling tools 88 provide the desired shielding required for plantpersonnel to work while standing on the shield plate.

FIG. 7 shows the decoupling tool 88 lowered until it engages the driverod 50. FIG. 8 shows where the decoupling tool 88 decouples the driverod 50 from the rod cluster control assembly 72 using methods that havealready been deployed in the operating fleet of pressurized waterreactors. Once decoupled from the rod cluster control assembly 72 thedrive rod 50 is raised using the hoist 90 and secured to the tubularpenetration 84 supporting the decoupling tool with the retaining clip92. The drive rod 50 will remain secure in this position through theremainder of the refueling activities. The rod cluster control assemblyremains in the fuel assembly and is moved with the fuel.

A shielded cylinder 106 is then lowered over the integral shield platelifting rig assembly 76 (shown in FIG. 9). This shielded cylinder may besupported by the structures within the containment building that supportthe reactor itself or it may be supported by its inwardly extendingupper flange 108 resting on the shield plate flange 102. The design ofthe shield cylinder 106 is such that it fits entirely around the upperinternals assembly 26 and the integral lifting rig 86 and has asufficient length to completely cover the length of the upper internals26 when the shielded cylinder's inwardly extending upward flange 108 isresting upon the shield plate flange 102 as shown in FIG. 10. A narrowedopening at the top of the shielded cylinder 106 formed from the inwardlyextending flange 108 allows both the upper internals and the shieldedcylinder to be lifted from the reactor vessel when the shielded plateflange 102 engages the shielded cylinder flange 108 as shown in FIG. 10.After the lifting fixture 76 engages the shielded cylinder 106 and theupper internals 26 has cleared the reactor vessel, the entire assemblyis moved to its refueling storage location. While the upper internals 26are being raised, the activated structures of the internals will breakthe water surface 96 and the potential for the creation of airborneradioactive contaminants exists as the components begin to dry out. Theintegral ventilation and filtration system 94 ensure that any airbornecontaminants are kept within the shielded cylinder by maintaining anegative atmosphere (i.e., the pressure within the shielded cylinder 106is below the pressure outside the shielded cylinder) or are captured inthe filtration system. FIG. 11 provides a three-dimensional perspectiveof the upper internals 26 captured within the shielded cylinder 106 andsupported by the shielded plate 78.

While this invention was described as applied to a small modular reactordesign, it should be appreciated that it can also be used in therefueling of conventional pressurized water reactors as well as othercompatible reactor designs. Dry refueling of conventional reactordesigns or reducing the extent of flooding that may be required duringrefueling will save time and expense on the critical path ofconventional plant refueling outages.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular embodiments disclosed are meant to be illustrative only andnot limiting as to the scope of the invention which is to be given thefull breadth of the appended claims and any and all equivalents thereof.

What is claimed is:
 1. A method of removing an upper internals packagefrom a nuclear reactor having a reactor vessel with an upper flangesurrounding an opening in the reactor vessel that is sealed by a matingflange on a closure head, the reactor vessel enclosing the upperinternals package that seats above a plurality of fuel assemblies withina core of the reactor, the upper internals package including a pluralityof rod travel housings in which control rod assembly drive rods arehoused and through which the drive rods travel along a vertical path,the method comprising the steps of: removing the closure head from thereactor vessel; lowering a shield plate over the opening in the reactorvessel after removing the closure head from the reactor vessel, theshield plate being sized to cover the opening when supported on thereactor vessel upper flange and being formed from a material thatlessens the radiation exposure of workers working above the shield platecovering the reactor vessel opening, with openings through the shieldplate in-line with the rod travel housings through which the control rodassembly drive rods can be accessed, the shield plate including anintegral lifting rig extending above an upper surface thereof; attachingthe shield plate to the upper internals package; accessing the controlrod assembly drive rods through the openings; and raising the shieldplate to withdraw the upper internals package out of the reactor.
 2. Themethod of claim 1 wherein the access openings include a drive rodlatching tool that is reciprocally moveable along a substantiallyvertical travel path through the opening and into the rod travelhousings to connect to the drive rods and decouple the drive rods fromthe corresponding control rod assemblies, including the steps of:attaching the drive rod latching tool to at least one of the drive rods;decoupling the drive rod from the corresponding control rod assembly;and raising the drive rod latching tool to raise the drive rod withinthe rod travel housing.
 3. The method of claim 2 including the step oflatching the drive rod in a raised position within the rod travelhousing after the raising step.
 4. The method of claim 2 wherein beforethe step of raising the shield plate the method comprises the step oflowering a shield cylinder over the shield plate and around the upperinternals package.
 5. The method of claim 4 including the step ofsupporting the shield cylinder from the shield plate when the shieldcylinder is fully lowered around the upper internals package.
 6. Themethod of claim 4 including the step of maintaining a negativeatmosphere within the shield cylinder.
 7. The method of claim 6 whereinthe step of maintaining a negative atmosphere within the shield cylindercomprises venting air within the shield cylinder and filtering thevented air before being exhausted outside the shield cylinder.